1. Field of the Invention
The present invention lies in the field of life support systems, and more specifically concerns the systems which affect and control the air breathed by human beings within an enclosure. It has broad application to any "air conditioning" system which includes a suction or vacuum subsystem, and has particular application to spacecraft and other interplanetary and planet-orbiting vehicles, operating in a vacuum or rarefied atmosphere. Even more specifically, the invention deals with methods and means for reducing the concentration of carbon dioxide (CO.sub.2) in a flowing breathable airstream, and also removing excess moisture from the airstream, and at the same time not affecting the control of the temperature of said airstream.
2. Description of the Prior Art
One known technique for scrubbing CO.sub.2 out of an airflow is by filtering the air through a chemisorbent material such as lithium hydroxide (LiOH). While this technique is feasible under certain circumstances, it has the major disadvantage that the LiOH filter is not regenerable; a permanent, non-reversable reaction takes place, with the result that the material is consumed and must be discarded and replaced with fresh material. This disadvantage is particularly obnoxious in a space craft, as it exacts a considerable weight penalty; the larger the crew, the more filter material must be packed into the ship at launch time. Also, the use of a non-regenerable filter material limits the space mission in various other respects, e.g., the duration of the flight and the other equipment which must be limited to make room for the consumable filter material.
In the same prior art system, it has been common to remove excess moisture from the breathable air by passing it through a condensing heat exchanger. Again a weight penalty is paid, and in addition there is a waste of energy. Some means is desired to make the CO.sub.2 scrubber material usable over and over again and, as a side benefit, to extract H.sub.2 O at the same time. It is also desirable not to be obliged to supply heat to one part of the system or to remove it from another, as each of these steps implies the need for additional equipment and materials, and such equipment and materials extract another weight penalty.